Like buttwarmers said, it's pretty impossible to know without seeing your box. "Rainbow team" is far too general of a term to really know what you're working with.

Are you playing ADQXQ? Are you playing Sakuya? Might you be play Ra or RaDra?

Maybe you're playing a real rainbow team like Fenrir.

We can't really say much without seeing your box.

However, if you never show us your box and you just want "general" rainbow recommendations (if you can even do such a thing), here are some of my favorite rainbow subs and what godfest to get them in:

Kalis - Godfest Exclusives (almost any godfest)

Awoken Isis - Egyptian 1

Jormungandr - Farmable

Fenrir (for real men) - Buy 10 packs on 5x GFE and try to get three

There's also no such thing as a "frequency" of a godfest coming around. They come every two weeks but the featured pantheons are randomized so you really can't predict any kind of frequency for a specific one coming around.

So yeah, this advice is mostly useless but I'm just really bored and I have no idea why I'm still typing. Post your box and we could offer some actual help.